"This concept of creating electricity through synergistic cooperation is not new. However, much of this work is still in its nascent stages," assistant professor Seokheun Choi.
In a cell chamber of 90µL, researchers placed a mixed culture of phototrophic and heterotrophic bacteria. Phototrophic bacteria uses sunlight, carbon dioxide, and water to make its own energy, while heterotrophic bacteria must ‘feed’ on provided organic matter or phototrophic bacteria to survive.
While the cell was exposed to sunlight, an initial dose of ‘food’ was added to the chamber to stimulate growth of the heterotrophic bacteria. Through cellular respiration, the heterotrophic bacteria produced carbon dioxide waste, which was used by the phototrophic bacteria to start the symbiotic cycle.
After the cycle was established, researchers stopped adding additional food sources and there was enough phototrophic bacteria to sustain the metabolic processes of the heterotrophic bacteria. Those metabolic processes generated an electrical current of 8µA/cm2 for 13 days.
According to the team, the power was about 70 times greater than current produced by phototrophic bacteria alone.
"Heterotrophic bacteria-based fuel cells generate higher power, while photosynthetic microbial fuel cells provide self-sustainability. This is the best of both worlds, thus far," Choi said.
The cells could be used to provide power in remote or dangerous locations for low power items like health monitors and infrastructure diagnostic sensors.
"There are some challenges of using this technique," Choi said. "Balancing both microorganisms' growth to maximise the device performance and the need to make sure that this closed system will permanently generate power without additional maintenance are two we have found. Long-term experiments are needed."
